1. Field of the Invention
The present invention relates generally to a gas turbine engine and, more particularly, to a lightweight turbine bearing support assembly for withstanding radial and axial loads in a gas turbine engine.
2. Description of the Prior Art
A gas turbine engine of the turbofan type generally includes a forward fan and booster compressor, a middle core engine, and an aft low pressure power turbine. The core engine encompasses a compressor, a combustor and a high pressure turbine in a serial flow relationship. The compressor and high pressure turbine of the core engine are interconnected by a central shaft. The compressor is rotatably driven to compress air entering the core engine to a relatively high pressure. This high pressure air is then mixed with fuel in the combustor and ignited to form a high energy gas stream. This gas stream flows aft and passes through the high pressure turbine, rotatably driving it and the core engine shaft which, in turn, rotatably drives the compressor.
In the turbofan engine, the residual gas stream leaving the core engine high pressure turbine is expanded through a second turbine, which as mentioned above is the aft low pressure turbine. The aft low pressure turbine, in turn, drives the forward fan via a separate shaft which extends forwardly through the central shaft of the high pressure turbine rotor. Although some thrust is produced by the residual gas stream exiting the core engine, most of the thrust produced is generated by the forward fan.
The engine frame is often used to support the bearings of the engine's turbines. Conventional bearing support frames are heavy, adding to the weight and cost of the engine. Also, the frames are subject to thermal stresses, thermal gradients and generally require flowpath heat shields if subjected to hot flowpath gases. These frames are massive in order to withstand large radial and axial loads. Conventional frames generally have radial or tangential struts positioned by axially spaced outer and inner rings to form an annular type, load bearing heavy structure. To protect this ring-strut structure from flowpath hot gases, a heat shield is required. Generally this heat shield is approximately the same weight as the bearing support frame, and equally costly.
Consequently, a need exists for an alternative bearing support assembly which will avoid the abovementioned drawbacks of excessive weight and cost.